The muscle isozyme of glycogen phosphorylase (MGP)is developmentally and neurally regulated in rat muscle. A series ot deletion derivatives were generated in a CAT reporter vector to identify elements in the 5' noncoding region of MGP required for developmental regulation. A 269 bp fragment was identified that conferred 15-fold higher levels of CAT activity in C2C12 myotubes than myoblasts. This fragment contained four E box motifs located at -167, -118, -18 and +29, a CArG-like element (CCAAAATAGC) at -109, a GC rich region at -63 and a TATA motif 27 bp 5' of the transcriptional start point. Point mutations of the E boxes had little affect on the developmental regulation of MGP. Three of the muscle regulatory factor proteins (MyoD, myogenin and MRF4) transactivated the MGP promoter by only 2-fold and one them ( myf-5) had no effect on CAT activities in cotransfection studies in the nonmuscle cell line C3H10T1/2. Deletion of the CArG-like sequence reduced the difference between MT and MB CAT activity to only 1.8-fold. This may be a potential area of importance in the developmental-specific regulation of MGP in muscle cells. Further deletion of the GC motif eliminated any measurable CAT activity and defined the minimal promoter region between -76 and +3.
|Original language||English (US)|
|State||Published - 1996|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology